Reading in a binary file but looking for decimal character

I'm given code that reads in a file in binary. I can access any character in the
binary file as a position in an array, for example:

ReadFile thefile("TestFile.bin");

cout << thefile[3] << endl;

would output the 4th character in this binary file.

I need to read this file through, and output how many characters in it are of a
certain decimal value, for example, decimal value 65 == A.

How might I read in a binary file yet look for a decimal value? If a loop is used
checking thefile[i] reports back the actual character, not the
decimal value of that character. So I'm not sure how to count how many instances
of decimal 65 occur in the file?